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Dermpath-India Pathology of Desmoplastic Spitz Nevus
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Desmoplastic Spitz nevus (DSN) is a rare variant of spitzoid tumour which was first described by Reed et al. in 1975.
Desmoplastic Spitz nevus has clinical and histopathological features that are difficult to differentiate from dermatofibroma and desmoplastic malignant melanoma (DMM), which requires aggressive therapy for cure. It occurs most frequently in young adults and children. Desmoplastic Spitz nevus usually presents as a red-brown papule or nodule, located on the extremities. However, lesions on the abdomen, head and neck region and a case with multiple lesions have been reported.
Differential diagnosis: 1) Spitz nevus: It is differentiated from classical variants of Spitz nevi by lack of dermoepidermal activity, absence of Kamino bodies, increased dermal collagen and presence of ganglion-like epithelioid cells. 2) Dermatofibroma: The DSN can be mistaken for dermatofibroma due to similar location and clinical appearance. It can be differentiated precisely from dermatofibroma with the presence of melanocytes and the positive immunohistochemical staining of the cells with S-100 protein and antibody HMB-45. 3) Desmoplastic malignant melanoma: From a histopathological point of view, symmetry, circumscription, melanocytic maturation and involvement of adnexal structure are significantly more frequent in desmoplastic Spitz nevi. The presence of melanocytic junctional nests associated with discohesive cells, variations in size and shape of the nests, lentiginous melanocytic proliferation, actinic elastosis, pagetoid spread, dermal mitosis, perineural involvement and brisk inflammatory infiltrate are significantly more frequent in desmoplastic melanoma. No significant difference is found concerning epidermal hyperplasia, presence of Kamino bodies or moderate inflammatory infiltrate.
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